Ugly Droughts

How do recent droughts compare to 30 years ago?

The drought that settled over more than half of the U.S. last summer was the most widespread in more than 50 years, and now a long dry winter has set up farmers for a nail-biting spring.

Little in our lifetimes tops the 2012 drought disaster, which goes down as among the ten worst of the past century, according to a new report released by the National Climatic Data Center (NCDC). With records dating to 1895, NCDC’s State of the Climate shows only the extraordinary droughts of the 1930s and 1950s covered more land area than the 2012 drought. By a slight margin, last summer’s drought actually covered more land mass than the infamous 1936 drought.

However, when areas classified as "moderate" drought are excluded, the historical rankings change, notes Elwynn Taylor, Iowa State University climatologist. Some droughts were extremely intense, but focused on specific regions rather than sprawling across large swaths of the country.

For example, droughts in 1988, 2000 and 2002 included more than 35% of the U.S. in the "severe" to "extreme" drought categories on the Palmer Drought Severity Index. By comparison, severe to extreme drought covered 32.7% in June 2012.

The drought of 30 years ago was no slouch. The 1983 Midwest drought was associated with very dry conditions, severe heat and substandard crop growth, which affected prices and caused hardship for farmers. Multiple disaster declarations went out in Indiana and neighboring states. Readings of 100° F and higher became prevalent in 1983 during these dry spells across the Midwest, Ohio Valley and Great Lakes regions. The heat waves killed 500 to 700 people.

Heading into 2013. In an ironic end to a winter spent fretting about drought, late snows and heavy rains last month renewed the rising of Midwestern rivers. Current conditions show a change in deep soil moisture levels in the eastern U.S.

Nevertheless, drought situations today will have more impact on food prices than 30 years ago, to the tune of about $3.4 billion during the next year or two, says Paul Walsh, a weather analyst for The Weather Company and The Weather Channel. "It has a huge impact, particularly on winter wheat and areas like Colorado," Walsh says.

By March, Colorado had only seen 50% of its normal snowpack. "That affects agriculture dramatically because water from the snow pack services crops throughout the West."

Apples-to-Apples Drought Comparison Difficult

The Drought Monitor report debuted in 1999, and the period of detailed records began in January of 2000. One of the many inputs in the Drought Monitor report is the Palmer Drought Severity Index. This index, developed by meteorologist Wayne Palmer in the 1960s, uses mathematical equations incorporating precipitation and temperature data to estimate evaporation, runoff and soil moisture recharge.

The National Climatic Data Center maintains a database of monthly Palmer drought indices dating to 1895. Because of this much longer period of record, the Palmer index can be used as more of an "apples to apples" comparison between recent weather conditions and those from past decades, at least on a meteorological basis.

However, differences in land use and farming practices since the Dust Bowl make the comparison of real-world impacts more complicated. Erosion-control practices and drought-resistant crop hybrids are just two examples of ways in which modern agriculture attempts to mitigate the impacts of severe drought.